Parasteatoda

Parasteatoda species can be distinguished from the related genus Steatoda by abdominal shape—Parasteatoda has a more pronounced teardrop form with the anterior section distinctly higher than the carapace. The genus is further characterized by the male stridulatory apparatus and specific leg formula (1243 in males, 1423 in females). Species-level identification requires examination of genitalic structures and other detailed morphological features. Parasteatoda tepidariorum, the Common House Spider, is frequently misidentified as the Brown Widow (Latrodectus geometricus); the latter can be distinguished by the presence of a red or orange hourglass marking on the underside of the abdomen, which Parasteatoda lacks.

Species in this genus possess a characteristic teardrop-shaped or nearly spherical abdomen with the anterior section elevated above the carapace and spinnerets pointed downward. The abdomen exhibits highly variable coloration, ranging from greyish brown to blackish brown or bright orange, often with a broad longitudinal cardiac pattern and transverse spots. The carapace is oval. Males possess a stridulating apparatus consisting of partial lunate plates on either side of the pedicel. Sexual dimorphism is slight, with males visually similar to females but somewhat smaller. Leg formula is 1243 in males and 1423 in females.

The genus is primarily Old World in distribution, with native species occupying diverse habitats across Asia, New Guinea, and parts of Europe. Several species, notably Parasteatoda tepidariorum, have become synanthropic and are strongly associated with human habitations, found under eaves, in window wells, rock retaining walls, and tree holes. These introduced populations thrive in built environments and are seldom found in natural settings.

Native range encompasses Asia, New Guinea, and parts of Europe. The genus has become increasingly widespread in the Americas and Europe due to human-mediated introduction of several species. Parasteatoda tepidariorum specifically has achieved cosmopolitan distribution through global commerce, with suspected South American origin despite initial description from German specimens.

• Zatypota albicoxa - ectoparasitoidIchneumonid wasp that parasitizes Parasteatoda tepidariorum in southwestern Japan

For Parasteatoda tepidariorum: Females produce numerous tan, papery, pear-shaped egg sacs from late spring through late summer, each containing 100–600+ eggs. In laboratory conditions at 25°C, eggs hatch in approximately 7 days. Juveniles undergo several molts over 2–3 months to reach sexual maturity. Mated females can repeat egg production cycles every 4–6 days without remating, producing up to ~10 egg sacs. The species exhibits diapause under short-day conditions.

Parasteatoda tepidariorum exhibits complex behaviors including nest-building, predation, courtship, and egg care. Females engage in web-twanging behavior that appears to advertise receptivity and leads to successful matings. Cannibalism occurs among juveniles from single egg sacs. Males may share female webs. Females are largely sedentary on their webs while males are more active walkers. Re-mating rates are low in this genus, with most females mating only once regardless of whether encounters are with the same or different males.

As members of family Theridiidae, Parasteatoda species function as generalist predators of insects and other small arthropods. In urban environments, P. tepidariorum occupies building surfaces as a microhabitat specialist. The genus contributes to spider conservation in urban landscapes, with P. tepidariorum specifically classified as a space-web weaving guild member that benefits from scale-infested trees and associated prey communities.

Parasteatoda tepidariorum, the Common House Spider, is one of the most familiar spiders in human dwellings across much of the world and serves as an important model organism for evolutionary developmental biology research. Its genome has been sequenced, revealing whole genome duplication within chelicerates. The species is not considered dangerously venomous to humans or pets, though it is frequently misidentified as the venomous Brown Widow. Other species in the genus have been introduced to new regions through human commerce and are becoming more widespread.

• SteatodaRelated theridiid genus; Parasteatoda differs in having more pronounced teardrop-shaped abdomen with anterior elevation, distinct leg formula, and male stridulatory apparatus
• LatrodectusBrown Widow and related widows share family Theridiidae and similar web architecture; distinguished by presence of red/orange hourglass marking on abdomen underside (absent in Parasteatoda) and more potent venom
• AchaearaneaHistorical taxonomic confusion—P. tepidariorum was placed in this genus by Levi in 1955, but current taxonomy places it in Parasteatoda based on morphological and phylogenetic evidence

• cobweb weaver
• comb-footed spider
• model organism
• synanthropic
• cosmopolitan
• Old World genus

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Spider Sunday: Common House Spider
• Bug Eric: March 2012
• Bug Eric: Spider Sunday: Brown Widow
• Bug Eric: One Night, One House, Seventeen Spider Species
• Scale Insects on Urban Trees Benefit Spiders, Other Natural Enemies in Plants Below
• Bug Eric: Spider Sunday: Triangulate Cobweb Weaver
• The common house spider Parasteatoda tepidariorum
• Evolutionary crossroads in developmental biology: the spiderParasteatoda tepidariorum
• Primary cell culture from embryos of the common house spider Parasteatoda tepidariorum
• The mating system of the common house spider Parasteatoda tepidariorum
• Seasonal Life Cycle ofZatypota albicoxa(Hymenoptera: Ichneumonidae), an Ectoparasitoid ofParasteatoda tepidariorum(Araneae: Theridiidae), in Southwestern Japan
• Female mating rates and their fitness consequences in the common house spider Parasteatoda tepidariorum